Sunnovations’ Ohm SWH Production Meter

The ohm is a familiar unit for measuring electrical resistance It’s also a new solar heating monitor from solar water heating manufacturer Sunnovations (ohm.sunnovations.com). The Ohm is a production meter for residential use that eliminates the need and costs of an inline flow meter. The Ohm uses a resistance temperature device to measure the tank temperature and calculate the gain for each day. The Ohm requires Internet access at your home and uses a third-party website to access monitoring data. The company has published on its website the results of independent testing of the unit’s accuracy.

Of course temperatures vary within a tank and device location also comes into play so getting true measurements of daily gain can be questionable. Add owner usage which reintroduces cold water into the tank at variable temperatures to the mix also.
When it all comes down to it, you gain what you gain and there is nothing you can really do about it, unless you have some kind of control for the sun and clouds.
I know there are those who like to see some kind of numbers applied to a system to satisfy their desires to see just how much money they are saving but the best way they can see this is to look at their utility bills.
Does the device also account for loses within the system?
Not that I am totally against monitoring, I just don't feel the added cost is justified, especially when it is savings that one is looking for.